Oscillation maintenance method for mechanical resonator and related apparatus

ABSTRACT

A technique is provided for oscillation maintenance in mechanical resonators of the type actuated by electric pulses transmitted by a coil to a permanent magnet carried by the resonator or conversely, the oscillation frequency of the resonator being modified by the action of a spring repelling it elastically on both sides of its resting position. Starting from a train of chopped (contact-modulated) square-wave pulses varying according to a tempo corresponding to a pilot frequency f in such manner that, for each succeeding alternation of this latter, the pulses are divided so as to correspond alternatively to one of two energies of different levels. The voltages induced by the resonator magnet in the induction coil is compared to the aforesaid pulse train and so acts that each successive alternation of a given signal of said voltage, beyond a preset threshold, triggers the transmission to the induction coil of a maintenance energy of the value contained in the equivalent section of the pulse train. The purpose is to establish a state of synchronism between the pilot frequency f and that of the mechanical oscillation.

United States Patent ,[191

Berney Apr. 16, 1974 OSCILLATION MAINTENANCE METHOD FOR MECHANICAL RESONATOR AND RELATED APPARATUS Jean-Claude Berney, Lausanne, Switzerland [75] Inventor:

[73] Assignee: Bernard Golay S.A., Lausanne,

Switzerland Filed: Sept. 25, 1972 Appl. No.: 292,166

US. Cl 331/1 A, 331/116 M Int. Cl. H03b 3/04 Field of Search 331/1 A, 20, 19, 116 M [56] References Cited UNITED STATES PATENTS 3,512,351 5/1970 Shelley et al 331/116 M Primary Examiner-John Kominski Attorney, Agent, or Firm-Eric l-l. Waters 3/1960 Salmet 331/19 1 [5 7] ABSTRACT A technique is provided for oscillation maintenance in mechanical resonators of the type actuated by electric pulses transmitted by a coil to a permanent magnet carried by the resonator or conversely, the oscillation frequency of the resonator being modified by the action of a spring repelling it elastically on both sides of its resting position. Starting from a train of chopped (contact-modulated) square-wave pulses varying according to a tempo corresponding to a pilot frequency f in such manner that, for each succeeding alternation of this latter, the pulses are divided so as to correspond alternatively to one of two energies of different levels. The voltages induced by the resonator magnet in the induction coil is compared to the aforesaid pulse train and so acts that each successive alternation of a given signal of said voltage, beyond a preset threshold, triggers the transmission to the induction coil of a maintenance energy of the value contained in the equivalent section of the pulse train. The purpose is to establish a state of synchronism between the pilot frequency f and that of the mechanical oscillation. I

ufi la zaao fi Brewi g F e PATENTEDAPR 16 I974 SHEEI 1 0F 3 OSCILLATION MAINTENANCE METHOD FOR MECHANICAL RESONATOR AND RELATED APPARATUS FIELD OF INVENTION The present invention relates to an oscillation maintenance method and apparatus for mechanical resonators of the type actuatedby electric pulses transmitted by an induction coil to a permanent magnet carried by the resonator or conversely, the oscillation frequency of this latter being moreover modified under the action of means repelling it elastically on both sides of its resting position.

SUMMARY OF INVENTION An object of this invention is to provide an improved apparatus and method to maintain resonator oscillations in synchronism with a pilot frequency f.

For this purpose, the invention provides for starting from a train of chopped (contact-modulated) squarewave pulses varying in accordance with a tempo corresponding to the pilot frequency f in such manner that, for each successive alternation thereof, the said pulses are divided to correspond alternatively to one of two energies of different levels, since the voltage induced by the resonator magnet in the induction coil is compared to the aforesaid pulse train and acts in such a way that each successive alternation of a given sign of said voltage, beyond a preset threshold, triggers the transmission to the induction coil of a maintenance energy of the value included in the equivalent section of the pulse train.

Considered in another aspect the invention provides a method for maintaining oscillation in a mechanical resonator actuated by energy exchanged between a coil and a magnet carried by said resonator, said method comprising determining the deviation between squarewave and sine-wave signals representing a standard and the movement of said resonator, said deviation dividing the cycles of the sine-wave signal into separate parts during each of which respectively different levels of maintenance energy are delivered to said coil whereby the resonator is synchronized with the sine-wave signal.

According to a feature of the invention the different levels of energy may be provided by the use of different duty cycles.

According to another aspect of the invention, two different duty cycles pulse lengths are prepared by the combining of three frequencies related to the frequency of the square-wave signal.

As to the apparatus, in combination with apparatus including a resonator, a magnet on said resonator, a coil to exchange energy with said magnet, and spring means to limit oscillation of said resonator, there is an oscillation maintenance circuit comprising a source of regularly shaped pulses at a standard frequency, means to derive a sine-wave signal from said coil, means to compare the phases of the regularly shaped pulses and said sine-wave signal such that the pulses are divided into separate sections and means to supply respectively different energy levels to said coil during said different sections.

According to a feature of the invention a noted above the pulses may be square-wave pulses.

According to a further aspect of the invention there will be provided a source of pilot frequency squarewave pulses and further sources of square-wave pulses, one of which is a multiple of the frequency of the other, and means to combine the latter said pulses to produce pulses of different duty cycles and thereby of different energy levels.

The aforesaid means may include a NOR gate, three NAND gates, one of which couples the other two to said NOR gate, a further NAND gate, an inverter, said further gate being respectively coupled directly to one of said other gates via said inverter to the other of said other gates, said source of pilot frequency pulses being coupled to said one of said other gate and a second inverter coupling the latter said source to said other of said other gates, said further sources being coupled to said further gate.

According to another aspect of the invention, there may be provided first and second transistors, a capacitor, first and second resistors and a third inverter. Said first transistor is coupled between said coil and ground and said capacitor and second transistor are coupled across said coil. Said first resistor is connected between the junction of the capacitor and second transistor and ground. Said second resistor is connected between the second transistor and ground. Said third inverter is connected between the junction of said second transistor and said second resistor and said NOR gate.

BRIEF DESCRIPTION OF DRAWING The attached drawing shows one embodiment of the invention, given by way of example.

In the drawing:

FIGS. 1 and 2 are a vertical section along the axis and a plan view respectively of a mechanical resonator provided in accordance with one embodiment of the invention;

FIGS. 3 through 8 are wave form diagrams explaining the principle which is the basis of the invention;

FIG. 9 is a logical diagram of an electronic layout for the operation of the invention; and

FIG. 10 illustrates the voltage curves explaining the chopping of the pilot frequency f DETAILED DESCRIPTION The type of resonator given by way of example in FIGS. 1 and 2 is a watch movement balance. The present invention is not, however, applied exclusively to this mechanical field but can be applied to any mechanical resonator fulfilling the conditions of oscillation described hereinafter.

As shown, a balance 1 is provided in the shape of a beam turning on a shaft 2 under the action of electric pulses transmitted to it by the winding of an induction coil 3 acting on a magnet 4 carried by the said beam whichlast is connected to a hairspring 5.

The magnet 4 is so arranged as to be located, when the hairspring is at rest, between the armatures 6 of the electromagnet composed of the induction coil 3 and its core 7. The whole structure is arranged between a plate 8 and a bridge 9.

The beam carries a pin 10 which, when its oscillations overstep a preset angle, meets and is driven back by a flexible blade 11.

It follows that, on each transit of magnet 4 between the armatures 6, it induces a sine wave voltage in coil 7. Such voltage increases, reaches a maximum then decreases when the magnet moves away from the magnetic circuit. According to the invention, it is compared to a square-wave pulse of frequencyfwith which it is to be synchronized while transmitting to the inducing electromagnet 3 6 a variable energy suitable for producing such synchronization.

FIGS. 3 through 8 illustrate the principle suggested for attaining such result.

FIG. 3 shows the sinusoidal wave 12 constituting the signal induced in coil 3 by magnet 4 and facing the square-wave pilot pulses 13 of frequency f. Signal and pulse are, as illustrated in the figure, perfectly synchronized, and all that is required is to transmit a relatively low maintenance energy to the resonator.

This is obtained, in accordance with the corresponding FIG. 4, by chopping the square pulse so as to preserve, in the example shown, only one quarter, indicated by the strips 14 which are further made to act only beyond a certain threshold 15 of signal 12.

In the case of FIG. 5, similar to FIG. 3, the signal 12 is generated during the second (negative) alternation of the square pulse 13 of frequency f. It will then be necessary to supply a relatively large energy to the electromagnet 3 6 allowing the resonator to speed up for the purpose of getting it back into synchronism.

This is obtained, in accordance with the corresponding FIG. 6, by chopping the square-wave pulse so as to preserve three quarters of it in the example shown, as indicated by the strips 16 representing an energy three times that transmitted in accordance with FIG. 4 and, equally, beyond a threshold 15.

In acting so that each semi-alternation of the squarewave pulse triggers bring about the release of an energy alternately in a ratio of one to three. An uninterrupted train of energy pulses of duty cycles or pulse lengths E and 3E is thus obtained (in the example shown), of which each value is spread over a portion of the alternations of frequency f.

This wave train compared to the signal in any phaseshifted position of these two curves leads in the most general case to the result shown in FIGS. 7 and 8.

FIG. 7 brings out a phase shift of angle a between signal 12 of the square-wave pulse 13. The result will be that the resonator will, in the present instance, receive an energy 3E during the fraction 0: of its oscillations semiperiod and an energy E during the fraction (1 of its oscillations semiperiod, an energy whose total 3., E +a E will help to reestablish the synchronic state.

Finally it should be noted that the drive pulses having to be unidirectional, will be activated, as will shortly be seen, by the current induced by the resonator oscillations.

There is a preferred equipment layout whereby the above-described results are obtained. It is shown by FIG. 9, granting that recourse is again had to a division of the maintenance energy in the ratio of 1 quarter to 3 quarters.

Three alternative sources of current are provided for supplying square-wave pulses.

One source 17 supplies the pulses of an agreed pilot frequency of 2 cs.

Two other sources 18 and 19 supply a frequency of 1024 cs and 512 cs respectively and are connectedto a NAND gate 20. k

The other NAND gates 21 and 22 follow controlled by the frequency 2 cs. One gate 21 is controlled directly, the other gate 22 is controlled through an inverter 23. The output of the NAND gate 20 is also connected to the two NAND gates 21 and 22, namely directly for the gate 21 and through an inverter 24 for gate 22.

The outputs of these two gates 21 and 22 are finally connected to the NAND gate 25, whose output is the source of the chopped pulses.

These act, from the output of this last gate, on a NOR gate 26, whose output in its turn controls the maintenance transistor 27 of the induction coil 3.

There next follows an explanation of how the illustrated electronic chopper works:

FIG. 10 shows four curves, of which curves A and B represent the square-wave pulses of frequency 512 cs and 1024 cs respectively, there being a ratio of l to 2 between these frequencies.

These pulses expressed in logical values travel alternately from O to 1. FIG. 9 showed that these were ap plied to the NAND gate 20.

It is known that the logic of such a gate is as follows:

From a comparison or superposition of curves A and B from FIG. 10, it can be deduced that the output of the said gate 20 will have the appearance of curve C. This curve displays successively the logical value 0 during l/4th of each period and the logical value I during the 3/4ths of the period. That is, the chopped voltage is applied at the input of the NAND gate of reference 21 at the same time as the pilot alternating voltage of frequency 2 cs in the example selected.

That same chopped voltage travels also through inverter 24, from whichit issues in the shape of curve D of FIG. 10, to be applied to the NAND gate 22 at the same time as the pilot alternating voltage, which is itself inverted by the inverter 24.

According to the logical rule enunciated above, gate 21 will allow the chopped signals to pass 3/4ths the time period of curve C whenever the logical value of the pilot frequency is 1. During an alternation of the pilot frequency and, consequently, on inversion by inverters 23 and 24, gate 22 will allow the chopped signals to pass l/4th the time period of curve D whenever the logical value of the pilot frequency is 0, that is, during the succeeding alternation of the pilot frequency, and so on.

These two series of signals are then applied to the NAND gate 25, where their superposition will give rise at the output of gate 25 to the wave train discussed above, equivalent to the quarter of the maximum possible energy during one alternation of the pilot frequency and to three quarters during the following alternation, and so on.

This wave train is now applied to the NOR gate 26, itself connected through inverter 28 to a control circuit placed under the influence of the induced pulses emitted by induction coil 3.

These pulses are transmitted through capacitor 29 to transistor 30, two resistances 31 and 32 being provided. Resistor 31 and the capacitor 29 have values sufficiently large for the transistor 30 to be biased to class operation and to function thus as a level detector. This is therefore the one whose assignment is to prevent passage of the pulses induced in coil 3 except when their value exceeds a certain level in FIGS. 3 through 8).

These pulses then arrive at gate 26 through the agency of inverter 28.

It is known that the logic of a NOR gate is:

Now, when the voltage induced in induction coil 3 exceeds, the triggering threshold of the level detector including transistor 30, the state at the input terminals of resistance 32 and of inverter 28 becomes a 1 and passes on the contrary to a O at the output of the inverter, this opening the NOR gate 26, allowing the output voltage of 25 to cross it and reach the master oscillator amplification MOS transistor 27.

A portion of the amplified square-wave pulse train, cut off so to speak, in the said sequence, will be transmitted to induction coil 3 in accordance with what has previously been described.

Obviously other frequencies than those of the example discussed can be selected and the electronic operations in question could be effected by other combinations of gates.

From what has been stated above, it will be seen that the above technique permits synchronization of a resonator (oscillating member) on which an isochronism fault has been previously and artificially created. The synchronization is thus obtained by a variation of the maintained energy which is itself known.

The present process is, however, distinctive in that this energy is obtained by the utilization of a train of impulses of high frequency and without direct coupling with or reference to the frequency of the resonator.

The length of each of the impulses forming this train is modulated by the reference frequency f between two corresponding values, one at positive alternance, the other at negative alternance of this frequency f. In FIG. 9, this train of impulses is produced by the elements 25. This train of impulses is only applied to the motor coil of the resonator when the induced voltage at the terminals thereof exceeds a predetermined value.

The energy thus received by said motor coil thereby depends solely on the length of each of the impulses of the train applied thereto, or thus indirectly to the refer ence frequencyf. Consequently, there is never a direct comparison between this frequency f and the oscillation frequency of the resonator.

What is claimed is:

l. A method for maintaining oscillation in a mechani cal resonator actuated by energy exchanged between a coil and a magnet carried by said resonator, said method comprising utilizing the deviation between a reference signal and a sine wave signal respectively representing a standard and the movement of said resonator, said deviation being used for controlling the delivery of respectively different levels of maintenance energy to said coil whereby the resonator is synchronized with the standard, the different levels of energy being provided by the delivery to said coil of trains of pulses wherein the pulse lengths are controlled by said deviation.

2. A method as claimed in claim 1 wherein the different pulse lengths are prepared by the combining of signals of two frequencies related to each other.

3. In combination with apparatus including a resonator, a magnet on said resonator, a coil to exchange energy with said magnet, and a stop to limit oscillation of said resonator, an oscillation maintenance circuit comprising a source of regularly shaped pulses at a standard frequency, means to derive a sine wave signal from said coil, a source of pulses of different pulse lengths, means to determine deviations between the regularly shaped pulses and said sine wave signal, and means to supply to said coil pulse trains consisting of the pulses having said different pulse lengths and in accordance with said deviations.

4. A circuit as claimed in claim 3 wherein the second said source includes sources of square-wave pulses one of which has a frequency which is a multiple of the frequency of the other, and means to combine the latter said pulses to produce pulses of different pulse lengths and thereby of different energy levels.

5. A circuit as claimed in claim 4 wherein the latter said means includes a NOR gate, three NAND gates one of which couples the other two to said NOR gate, a further NAND gate coupled directly to one of said other gates and via said inverter to the other of said other gates, the first said source of pulses being coupled to said one of said other gates, and second inverter coupling the latter said source to said other of said other gates, said sources of square-wave pulses being coupled to said further gate.

6. A circuit as claimed in claim 5 wherein the first, second and third said means cooperatively include first and second transistors, a capacitor, first and second resistors, and a third inverter, said first transistor being coupled between said coil and ground, said capacitor and second transistor being coupled across said coil, said first resistor being connected between the junction of the capacitor and second transistor and ground, said second resistor being connected between the second transistor and ground, said third inverter being connected between the junction of said second transistor and said second resistor and said NOR gate. 

1. A method for maintaining oscillation in a mechanical resonator actuated by energy exchanged between a coil and a magnet carried by said resonator, said method comprising utilizing the deviation between a reference signal and a sine wave signal respectively representing a standard and the movement of said resonator, said deviation being used for controlling the delivery of respectively different levels of maintenance energy to said coil whereby the resonator is synchronized with the standard, the different levels of energy being provided by the delivery to said coil of trains of pulses wherein the pulse lengths are controlled by said deviation.
 2. A method as claimed in claim 1 wherein the different pulse lengths are prepared by the combining of signals of two frequencies related to each other.
 3. In combination with apparatus including a resonator, a magnet on said resonator, a coil to exchange energy with said magnet, and a stop to limit oscillation of said resonator, an oscillation maintenance circuit comprising a source of regularly shaped pulses at a standard frequency, means to derive a sine wave signal from said coil, a source of pulses of different pulse lengths, means to determine deviations between the regularly shaped pulses and said sine wave signal, and means to supply to said coil pulse trains consisting of the pulses having said different pulse lengths and in accordance with said deviations.
 4. A circuit as claimed in claim 3 wherein the second said source includes sources of square-wave pulses one of which has a frequency which is a multiple of the frequency of the other, and means to combine the latter said pulses to produce pulses of different pulse lengths and thereby of different energy levels.
 5. A circuit as claimed in claim 4 wherein the latter said means includes a NOR gate, three NAND gates one of which couples the other two to said NOR gate, a further NAND gate coupled directly to one of said other gates and via said inverter to the other of said other gates, the first said source of pulses being coupled to said one of said other gates, and second inverter coupling the latter said source to said other of said other gates, said sources of square-wave pulses being coupled to said further gate.
 6. A circuit as claimed in claim 5 wherein the first, second and third said means cooperatively include first and second transistors, a capacitor, first and second resistors, and a third inverter, said first transistor being coupled between said coil and ground, said capacitor and second transistor being coupled across said coil, said first resistor being connected between the junction of the capacitor and second transistor and ground, said second resistor being connected between the second transistor and ground, said third inverter being connected between the junction of said second transistor and said second resistor and said NOR gate. 